VAwS (Ordinance on Installations for Handling Water-Polluting
Substances) – Specialist Company BQS 8.1, SKZ/TÜV-LGA
Quality guidelines for pipes, shafts and components in landfills

Project 01


PROJECT 01/2013 - Rehabilitation of the ventilation ducts of a phosphate plant in the automotive industry

Kunde: Automobilindustrie. Projektzeitraum Oktober bis Dezember 2013


In a phosphate plant, aluminium, magnesium, steel and zinc components are provided with a phosphate coating, which guarantees good paint adhesion and rust protection. The following usually occurs in the phosphate process: The component surface is degreased with a weak alkaline degreasing solution, rinsed, activated to form crystallisation nuclei for the phosphate layer, then phosphated with an acidic phosphate solution, rinsed, passivated and rinsed again. A titanium polyphosphate solution can be used for activation. The acidic phosphate solution may be a zinc, manganese and nickel phosphate solution, for example, containing an accelerator, such as nitrite.


The existing ventilation ducts made of galvanised sheet steel are heavily corroded and no longer withstand the aggressive exhaust air from the phosphate process which is distributed in various industrial halls. The project objective is to select a durable resistant and flame-retardant material to exclude possible environmental impact and thus ensure sustainable process safety. In addition, certain parts of the ventilator line outside buildings are exposed to an additional UV stress.

Entlüftungskanäle Entlüftungskanäle Außenansicht

Image: Heavily corroded ventilation system made of galvanised sheet steel


Our concept consists of a comprehensive system solution from one source.

  • Material selection according to our customers’ product specification requirements.
  • Planning and design, development and construction from identically designed components made of plastic.
  • Project management, production and assembly
  • Installation, commissioning and quality assurance

When choosing the material, we decided on PP-s grey fire-retardant polypropylene (-5°C to 80°C) for inside the building and on black PE-HD UV-resistant polyethylene (-30°C to 70°C) for outside the building (e.g. for the chimney on the roof). The different components are measured on-site in order to make identical components made of plastic as special designs from semi-finished goods, or to weld new mouldings so that they can be easily and accurately installed as ventilation ducts on-site later on. In this way, all individual components, such as existing consoles, vents and roof penetrations can continue to be used in order to minimise the costs.


All necessary parts were first prefabricated as custom-made in our plastics workshop according to their own design plans. The plastic components were then prefabricated on the CNC portal mill, folded accordingly and welded using hot-gas string bead or extrusion welding. Our assembly teams then delivered the individual parts to the customer and dismantled the old corroded sheet steel parts. As it was not possible to use a crane, the exhaust chimneys had to be cut and removed piece by piece for this purpose and then replaced with the new plastic parts. Here, all the individual components and special designs for all the ventilation ducts were welded together on-site via hot-gas string bead and extrusion welding.

PP Kunstoff um Lüftungskanäle PP Kunstoff um Lüftungskanäle Innenansicht PP Kunststoff

Image: New ventilation ducts made of PP-s and PE-HD plastic


Hazardous environmental and employee exposure to aggressive media is excluded

  • Assurance of sustainable process safety
  • High degree of function safety through resistant material selection of PP-s and PE-HD.
  • Cost savings through possible reuse of existing components (through 1:1 reconstruction of the individual components, it was possible to reuse all existing consoles, vents and roof penetrations that were still functional)

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